For example, in the information recording medium, such as an optical disc, like a CD-ROM (Compact Disc-Read Only Memory), a CD-R (Compact Disc-Recordable), a DVD-ROM and the like, there are developed a multi-layer type (i.e. a dual layer type optical disc and so on), in which a plurality of recording layers are laminated on the same substrate. More specifically, such a dual layer type optical disc has a first recording layer (referred to as a “L0 layer” in this application), as the first layer, which is located on the front (i.e. a side closer to an optical pickup) as viewed from a laser light emission side in recording information by the information recording apparatus, and further has a semi-transparent reflective coating or film, located on the rear thereof (i.e. a side farther from the optical pickup). As the second recording layer, it has a second recording layer (referred to as a “L1 layer” in this application), located on the rear of the semitransparent reflective coating through a middle layer, such as an adhesive layer, and further has a reflective film located on the rear thereof. In preparing such a dual layer type information recording medium, the L0 layer and the L1 layer are individually formed and pasted in the end, to thereby prepare the dual layer type optical disc at a low cost.
In the information recording apparatus, such as a CD recorder and a DVD recorder, for recording information onto such a dual layer type optical disc, the record information is recorded into the L0 layer in a rewritable method or irreversible change recording method, by focusing (or irradiating) the laser light for recording onto the L0 layer. The record information is recorded into the L1 layer in a rewritable method or irreversible change recording method, by focusing the laser light onto the L1 layer.
Patent document 1: Japanese Patent Application Laid Open NO. 2002-352469